Portable communications devices, such as mobile telephones, personal digital assistants (PDA) handheld communicators, etc, are often provided with a rechargeable battery pack for supplying electrical power to the device during the operation thereof. Even if rechargable battery packs have become increasingly efficient, they inevitably run out of power sooner or later and therefore have to be recharged repeatedly. In a worst case scenario the battery pack runs out of electrical power just before the user of the communication device is about to make an important telephone call, such as an emergency call ("112" in Europe, "911" in the USA). If this undesired situation occurs, the user is unable to make the important call immediately and has to find an operative telephone elsewhere or, alter-natively, detach the empty battery pack and replace it with another battery pack with a sufficient level of charge.
Various solutions have been proposed for enhancing the operability of portable communication devices and allowing instant use also when the primary power source (e.g. the battery) is inoperative. For instance, in EP-A-0 409 819 it is suggested to provide a mobile telephone with an electrical dynamo driven by means of a toothed rod, which is actuated via a movable operating lever protruding from the mobile telephone housing. Another way of inputting mechanical energy and converting it to electrical power in a mobile telephone is shown in GB-A-2 307 143, wherein a rotary knob is used to wind a spring, which drives a rotary electrical generator. Furthermore, U.S. Pat. No. 5,363,445 relates to an auxiliary charging device for a mobile telephone, comprising a coil, a magnet, a revolving disc, a set of gears and an operating handle. The operating handle is manually pushed inward to rotate the gears, the revolving disc as well as the magnet to cause the coil to produce electrical current to be supplied to the mobile telephone, when the battery thereof has been consumed.
A similar mechanical power supply for mobile telephones is known from DE-A-32 11 114, a first embodiment of which comprises a crank-and-gear arrangement and a second embodiment of which is using a spring. FR-2 079 913 relates to a power supply for a portable transceiver, wherein a crank is used for driving an electrical generator. JP-A-08018466 discloses a portable radio for emergency use. The radio comprises an electrical dynamo and a permanent magnet arranged to be movable in a longitudinal direction inside the radio housing. By exerting the radio to a reciprocating movement (for instance by shaking the radio) the permanent magnet is subjected to a reciprocating movement inside the dynamo, wherein electrical current is generated for driving the radio without any electrical battery.
The above prior art solutions are all able to allow operation of the portable communication device without any need for an operative electrical battery. However, all solutions have a common drawback in that they are dependent on user-initiated actuation. In order to generate the required amount of electrical energy the user has to pull a handle, rotate a knob, shake the radio, etc.